Science & Technology in Action

10th Edition

Using Bacteria to make a Biomolecule

MSD

Interferon inhibits cell proliferation and so has anti-cancer properties. In order to make it DNA coding for interferon is introduced into E. coli bacteria which multiply and produce commercial quantities of interferon. The cells are regularly harvested and the interferon extracted. Genetic modification of the bacteria is necessary as otherwise they would destroy the interferon, a protein foreign to them.
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Contains the full lesson along with a supporting toolkit, including teachers’ notes.

Lesson excerpt

Introduction 
Bacteria are single-celled organisms with a relatively simple biochemistry. Advances in genetic engineering and recombinant DNA technology have made it possible to use them for the mass-production of useful biomolecules such as hormones, vitamins and medicines. Many of these compounds were formerly sourced from animals. Obtaining pure compounds in sufficient quantities was very difficult and expensive. Animal-derived biochemicals might not be completely effective in humans, an environment they were not made for. Adverse immune reactions could, and did, happen. 

About interferon 
The story of interferon began in the 1950s. Scientists were looking for antibiotics that would combat viruses at a time when many vaccines had yet to be developed. In 1957, Lindenmann and Isaacs inoculated chicken embryos with influenza virus and noted that, after a time, viral action was inhibited. The tissues were cleared of virus but, if influenza or other viruses were subsequently applied, the anti-viral property was found to have persisted. Interferon had been discovered. 

Time would show that there were many types of interferon. They are cytokines - types of glycoprotein, that are produced by cells in response to the presence of viruses and certain foreign chemicals. Their action is indirect, activating genes in neighbouring cells to make proteins that interfere with cell replication. Apoptosis in infected cells may be encouraged. 

Interferon mobilises cells of the immune system and can cause foreign cells (including cancer cells) to display MHC antigens (major histocompatibility complex) – making them easier targets for the body’s defences. Interferons-α and β are produced by all cells. Interferon-γ is produced by immune cells only, stimulating further immune action. It also stimulates expression by professional antigen-presenting cells; these cells kill foreign cells and display antigens from their victims on their own surfaces, enhancing the immune reaction. 

Interferons have anti-cancer properties, unsurprising as they inhibit cell proliferation. They can sometimes disrupt the enzyme action involved in tumour angiogenesis (the laying on of a blood supply). It must be stated that viruses and tumours have shown adaptations to interferon action. Tumours may employ different enzymes. Viruses may disrupt interferon receptors as well as producing chemicals to neutralise inhibitors of their replication process. Nevertheless, interferons are effective overall. They also have anti-bacterial properties and provide defence against other parasites. 

Quiz questions

  1. Interferon is produced during the clotting process at the site of a wound. false
  2. Transfer of genetic material between organisms does not happen in nature. false
  3. Bacteria never revert to their original state after genetic modification. true
  4. The majority of eukaryotic genes, in contrast to those found in prokaryotes, have introns. false
  5. E.coli are the only bacteria that can be successfully modified to produce interferon. true
  6. In a first-time viral infection, interferon is produced more quickly than antibodies. true
  7. Cytokines are secreted low-molecular weight proteins that regulate the immune response. true
  8. Interferons were being used clinically on a large scale within ten years of their discovery in 1957. false
  9. Inflammation is an immune response to harmful stimuli, not always infections, which can be modulated by interferons. true